The invention relates to a spacecraft which includes an acceleration pickup for determining accelerations of the spacecraft, and to a process and a device for determining the operational condition of mechanical apparatuses mounted to or in the spacecraft.
A plurality of apparatuses are mounted in and/or to spacecraft whose operational conditions must be continuously monitored. Knowledge of the operational conditions of said apparatuses is important for various reasons. The apparatuses produce various types of interferences which may affect, for example, highly sensitive scientific experiments and measurements. Monitoring of the operational conditions of the apparatuses may also serve for measuring the service hours and monitoring the overall functionality of the spacecraft. The operational conditions are monitored by measuring electrical and physical operating variables of the apparatuses which require a plurality of electrical components, such as pickups, transducers, data lines etc., which make monitoring of the apparatuses complicated and susceptible to interference and fault.
The present invention is directed to a spacecraft, and a process and a device for easily monitoring mechanical apparatuses in and/or on the spacecraft.
Spacecraft, such as scientific spacelabs, are provided with highly sensitive acceleration pickups capable of measuring even minimum accelerations of the spacecraft. Such acceleration pickups are essentially employed for detecting and recording the so-called microgravitation, i. e., accelerations in the range of fractions of the acceleration due to gravity (g=9.81 m/sec2), when scientific experiments are carried out at zero-gravity in order to accurately document the boundary conditions of the experiments in terms of the occurring accelerations. Besides the gravitation force and the counteracting centrifugal force, the vibrations of operating mechanical apparatuses produce measurable periodic accelerations of the spacecraft.
According to the invention the acceleration pickup is additionally used in the spacecraft to determine the operational condition of at least one mechanical apparatus mounted in and/or to the spacecraft. A mechanical apparatus is an apparatus which comprises a mechanical component, e. g. a motor, compressor or other mechanism, carrying out a mechanical movement which produces accelerations in the form of vibrations, oscillations, etc. Such accelerations are transmitted to the spracecraft body by mechanical coupling of the apparatus to the spacecraft so that the accelerations produced by the mechanical apparatus can be detected at a different location in the spacecraft by the acceleration pickup installed in or to the spacecraft body. The operational condition of the apparatus is thus determined by the acceleration pickup which determines whether or not accelerations typical of the mechanical apparatus exist.
In this way the operational condition of a mechanical apparatus can be determined by the existing acceleration pickups without any sensors having to be attached to the mechanical apparatus or without electrical operating variables of the apparatus having to be monitored. The detectable operational condition of an apparatus may be xe2x80x9cSwitched onxe2x80x9d, xe2x80x9cSwitched offxe2x80x9d, xe2x80x9cSlow modexe2x80x9d or xe2x80x9cFast modexe2x80x9d relative to the respective mechanical components of the apparatus. In this way monitoring of the operational condition of a mechanical apparatus is effected and does not require any direct electrical or electromagnetical connection to the apparatus and is thus completely independent of other control and operational information of the mechanical apparatus. This type of apparatus monitoring is thus easy to realize and extremely reliable due to its independence.
In a preferred embodiment of the invention detection of the operational condition of the apparatus is effected by a comparison of the occurring acceleration pattern or parameters derived therefrom with prestored acceleration patterns or parameters of the apparatus being monitored. The acceleration patterns may, for example, be stored as derived frequency spectra of the apparatus in operation. The measured acceleration curve of the spacecraft is split up into a frequency spectrum and compared with the stored acceleration patterns or frequency spectra of the apparatus with the aid of a computer-assisted pattern recognition software. The degree of conformity of the measured acceleration patterns or spectra with the prestored acceleration patterns or spectra indicates the operational condition of the apparatus.
Preferably the operational conditions of a plurality of apparatuses are monitored by a comparison of the occurring acceleration patterns with the prestored acceleration patterns of all apparatuses. In this way a single acceleration pickup is capable of simultaneously monitoring a plurality of apparatuses. The measured acceleration pattern and parameters derived therefrom are compared with the prestored acceleration patterns and parameters of all apparatuses being monitored. On the basis of conformity or nonconformity of the stored apparatus pattern with the detected acceleration pattern the operational conditions of a plurality of apparatuses can be determined.
When applying the process of the invention for determining the operational condition of a mechanical apparatus mounted to or in a spacecraft, first the acceleration of the spacecraft is measured, then an acceleration pattern of the spacecraft is determined from the measured acceleration values of the spacecraft and the detected acceleration pattern of the spacecraft is evaluated to ascertain the operational condition of the apparatus by comparing the determined acceleration pattern with known acceleration patterns of the apparatus. Thus, a process is provided which allows the operational condition of the apparatus, e. g., operation or nonoperation, to be determined without direct detection of operational variables of the apparatus. Furthermore, the process is designed to monitor the functioning of the apparatus independent of direct information from the apparatus.
Preferably this process serves for monitoring a plurality of apparatuses with the detected acceleration patterns of the spacecraft being compared with known acceleration patterns of all apparatuses and the respective operational condition of each apparatus being determined.
The device according to the invention for determining the operational condition of a mechanical apparatus mounted in or to the spacecraft comprises an acceleration pickup attachable to the spacecraft for measuring the acceleration of the spacecraft, and an operational condition determination device with a memory for storing known acceleration patterns of the apparatus, with the acceleration patterns of the spacecraft detected by the acceleration pickup being compared with the known acceleration patterns of the apparatus from the memory and the operational condition of the apparatus being determined on the basis of the degree of conformity of the two patterns.
Thus, the device detects the operational condition of the apparatus on the basis of the mechanical vibrations induced by the apparatus onto the spacecraft. The acceleration pickup detects both the acceleration acting upon the spacecraft from outside and caused by the gravitation force and the centrifugal force, and the accelerations of the spacecraft body produced by the apparatuses mounted to or in the spacecraft, which normally occur in the form of vibrations and oscillations having specific patterns and frequencies.
To determine the operational condition of the apparatus, parameters derived from the acceleration patterns, e. g., time-resolved frequency spectra, may be compared with each other.
Preferably an acceleration pickup comprises three acceleration detectors which detect the accelerations of the three space axes.
In a preferred embodiment of the invention the device for monitoring a plurality of apparatuses is configured in such a way that the determination device compares the acceleration patterns of the spacecraft with the known acceleration patterns of the apparatuses stored in the memory and determines therefrom the respective operational condition of each apparatus. In this way a single acceleration pickup can monitor the operational conditions of a plurality of apparatuses.
Preferably, a plurality of acceleration pickups is provided whose measured values are acquired and evaluated by the determination device for determining the operational condition of the apparatus. By the employment of a plurality of acceleration pickups even larger spacecraft can be monitored with detection gaps being avoided so that all apparatuses of the spacecraft producing vibrations are covered.
In a preferred embodiment of the invention the determination device is configured in such a way that it also determines the wear condition of the apparatus by comparing the acceleration patterns of the spacecraft with the known acceleration patterns of the apparatus. Wear of the apparatus frequently causes unbalances, frictional changes, etc. Such changes result in a change in the oscillatory response of the apparatus. The deviations in the oscillatory response are detected by the determination device and recognized as wear of the apparatus. In this way it is, for example, possible to carry out maintenance of the apparatus in dependence on the wear and an imminent apparatus failure can be recognized in due time.
Preferably, the determination device is capable of receiving operating data of the apparatus, which are also evaluated by the determination device to determine the operational and wear conditions of the apparatus. The determination device is supplied, for example, with electrical operating data and parameters of the apparatus besides the acceleration patterns so that determination of the operational and wear conditions can be realized with high reliability and redundance.
In a preferred embodiment of the invention a transmission device is utilized for wireless transmission of the operational and wear conditions of the apparatus, as ascertained by the determination device to a receiving device. The transmission device is capable of transmitting the information on the determined operational conditions, for example, from the spacecraft to a receiving device on earth so that the transmitted information can be further evaluated.
In a preferred embodiment of the invention a recording device for continuous recording of the acceleration values of the spacecraft is provided. In this way the acceleration acting from outside on the spacecraft can be documented so that during scientific experiments the boundary conditions regarding the prevailing acceleration are always known and can be reconstructed after completion of the experiments.